California officially became the first state in the nation on Wednesday, Dec. 5 to require homes built in 2020 and later be solar powered.

To a smattering of applause, the California Building Standards Commission voted unanimously to add energy standards approved last May by another panel to the state building code.

Two commissioners and several public speakers lauded the new code as “a historic undertaking” and a model for the nation.

“These provisions really are historic and will be a beacon of light for the rest of the country,” said Kent Sasaki, a structural engineer and one of six commissioners voting for the new energy code. “(It’s) the beginning of substantial improvement in how we produce energy and reduce the consumption of fossil fuels.”

The new provisions are expected to dramatically boost the number of rooftop solar panels in the Golden State. Last year, builders took out permits for more than 115,000 new homes — almost half of them for single-family homes.

Wednesday’s action upholds a May 9 vote by another body, the California Energy Commission, seeking to fulfill a decade-old goal to make the state reliant on cleaner, alternative energy. The energy panel’s vote was subject to final approval by the Building Standards Commission.

The Building Standards Commission was limited to reviewing the energy panel’s rulemaking process, not the content of the standards, said commission Chairwoman Marybel Batjer. Commissioners said the process was more than sufficient, with 35 meetings, hearings and webinars held over a 15-month period. The energy panel received more than 3,000 comments from over 100 stakeholders, officials said.

While nobody spoke Wednesday in opposition to the new provisions, the commission received more than 300 letters from around the state opposing the solar mandate because of the added cost.

Energy officials estimated the provisions will add $10,000 to the cost of building a single-family home, about $8,400 from adding solar and about $1,500 for making homes more energy-efficient. But those costs would be offset by lower utility bills over the 30-year lifespan of the solar panels.

One commission member worried the mandate would make it harder for California wildfire victims to rebuild, but supporters assured him that won’t be a problem.

Homeowners will have two options that eliminate the upfront costs of adding solar: Leasing the solar panels or signing a “power purchase agreement” that pays for the electricity without buying the panels, said Drew Bohan, executive director of the California Energy Commission.

One solar-industry representative said the net savings from adding solar power will be around $40 a month or nearly $500 a year.

“These standards won’t necessarily make homes more expensive to buy. What they will do is save money on utility costs,” said Pierre Delforge, a senior scientist with the Natural Resources Defense Council. “This is not only the right thing to do for the climate, it is financially smart.”

Meanwhile, the changes won endorsements both from environmentalists and the California Building Industry Association.

“Six years ago, I was very fearful of this,” said Bob Raymer, technical director for the state building association. “But the very open arrangement that we have with the (energy commission) … brought us to the point where we can support this.”

Homebuilders have been preparing for years to meet a proposed requirement that all new homes be “net-zero,” meaning they would produce enough solar power to offset all electricity and natural gas consumed over the course of a year.

Provisions adopted Wednesday relaxed that goal a bit, requiring new homes only offset electricity used but not natural gas.

To meet net-zero energy goals, a typical house would need the capacity to produce 7 or 8 kilowatts of electricity, which wouldn’t be cost-effective, Raymer told the commission. But a modest amount of solar — producing about 3 kilowatts of power — would be cost-effective in all of California’s 16 climate zones.

In addition to the solar mandate, the new provisions tighten green homebuilding standards, with such requirements as thicker attic and wall insulation, more efficient windows and doors and improved ventilation systems. They also encourage developers to add battery storage and heat-pump water heaters to new homes.

But the heart of the update is the solar power requirement, which applies to all new residential buildings up to three stories high, including apartments. The code allows some exceptions, such as when the structures are in shady areas or when electricity rates already are lower than the cost of generating solar power.

The rules also allow for offsite solar production, so developments can build solar arrays feeding multiple homes or contract with utility-owned solar farms.

“We have lots of options,” said Raymer, the building industry’s technical director.

Hundreds of letters, most of them form letters, poured into the capital opposing the solar mandate.

The solar mandate “will be costly to homeowners in California and also eliminates personal choice,” said a letter signed by Butte County Treasurer-Tax Collector Peggy Moak. Moak said the tab for installing solar panels is a lot higher than the $8,400 estimate, “running more than $25,000.”

“With median home prices in California already more than double the national average, this decision will make it even more difficult for the average Californian to afford a home,” added a letter signed by Assemblyman James Gallagher, R-Yuba City.

Several solar industry representatives speaking Wednesday supported the provisions, including a representative of Tesla, which builds battery storage systems for homes.

“The homeowners will be able to save money from the day they walk in the door,” said Kelly Knutsen, technology advancement director for the California Solar & Storage Association. “This is a historical policy. California is leading the country in clean energy, clean air and fighting climate change, all while saving consumers money.”